1. Technical Field
The invention relates to data storage devices.
2. Related Art
Data storage devices (data log devices) that continuously obtain and record data on temperatures, vibrations, brightness, sounds, images and the like are known, and such data storage devices are used in, for example, temperature management of foods, drive recorders, flight recorders, voice recorders, seismometers, and the like.
In these data storage devices, when values of measured data exceed a predetermined range, it can be judged that a certain event has occurred on the subject being measured. By conducting an analysis processing on data obtained after the aforementioned data, the situation of the subject after the occurrence of the event can be learned. Also, by conducting an analysis processing on data for a certain period of time preceding the event, the situation of the subject before the occurrence of the event can be learned. Japanese laid-open patent application JP-A-2005-259041 may be an example of related art.
When the time interval for measuring (storing) data is made shorter in the data storage device, changes in the data can be accurately recorded. However, when the time interval for measuring data is shorter, the number of data increases, and a memory with a greater storage capacity is required for recording the data.
In contrast, when the time interval for measuring data is made longer, the number of data sets is reduced, and a memory with a smaller storage capacity can be used. However, the longer the time interval for measuring data, the more difficult it becomes to record minute changes in the data.
Also, in order to know the situation about the occurrence of the event, changes in the data before and after the occurrence of the event may preferably be analyzed. However, it is necessary to record data constantly to secure storage of measured data before and after the occurrence of the event, which requires a memory with a large storage capacity.